Forceps and tweezers have long been in use in the medical profession and known in the patent literature. With the advent of plastics materials and methods of injection molding, disposable forceps of molded plastics became common. Such forceps generally comprise a unitary element defining a pair of substantially rigid arms, each terminating in a jaw, connected at the end remote from the jaw by a resilient hinge member which serves to space the arms apart by about 15 degrees and acts as a fulcrum about which the arms can rotate. Compression of the arms causes the jaws to come together in order to grip an object and, on release of the compression forces, the resilience of the hinge member causes the jaws to open.
The jaws of the forceps generally define transversely extending teeth which are staggered so that intermeshing occurs when the jaws are brought together. The intermeshing first occurs at the extreme tips of the jaws and then, as continued force is applied, the teeth are brought into intermeshing relationship over the entire opposing surfaces of the jaws. However, because of the inherent resiliency of plastic suitable for making forceps, in use, the arms of many conventional forceps move laterally relative to one another, thereby reducing the effectiveness of gripping by the tool.
To overcome this problem, special aligning devices and jaw configurations were devised to assure positive mating of the article-gripping surfaces One such means comprises two pairs of opposed lugs on the arms which interengage in use, and is shown in U.S. Pat. No. 3,653,389 (Shannon). Another structure is shown in U.S. Pat. No. 3,906,957 (Weston) including a flexible connector attached between the forceps arms adjacent to the jaws.
Yet another alignment means consists of a pin on one arm adjacent the jaws and a socket in registration therewith on the other arm, as shown, for example, in U.S. Pat. Nos. 3,140,715 (Whitton), 3,265,068 (Holohan) and 3,367,336 (Eizenberg). However, providing such pin and socket elements creates a technical molding problem. Forceps are generally manufactured in a two part mold, the parts being perpendicular to the planes of the arms. After molding, one part is pulled away from the second in order to release the injection molded product which retains a parting line at the intersection of the two parts.
In order to provide apertures in the transverse direction, such as the sockets, a cam-actuated side core is required which moves in and out of engagement with the forceps in the mold. One such side core is required for each aperture in the finished product. Furthermore, since a side core moving in and out of engagement with the forceps in the mold is required for each forceps being produced, only four such forceps can be produced simultaneously. In addition, such molds, aside from being of higher initial cost, are operated with higher maintenance cost. Therefore, forceps of this design are relatively costly and complicated to produce.
Forceps having a pin and a non-apertured female engagement element were not contemplated using conventional molding techniques since they cannot be provided by conventional molds. A non-apertured recess extending at 90 degrees to the forceps arm cannot be generated by a side core because there is no room to remove the side core therefrom.
One method of overcoming this molding problem is described in U.S. Pat. No. 3,392,727 (Hanlon). Hanlon provides a forceps having a flexible connecting hinge which permits one of the arms to move with respect to the other through an angle of about 165 degrees. Thus, the forceps can be molded in a conventional two-part mold in a flat, outstretched orientation and later folded angularly about the connecting hinge into the operating orientation having an angle of about 15 degrees between the arms in the unflexed state. However, this method limits the type of plastic material from which the forceps can be made since not all plastics are bendable.